Catalytic Materials Enabled by a Programmable Assembly of Synthetic Polymers and Engineered Bacterial Spores

Leveraging the versatile properties of bacterial spores in materials

Inspired by biological functions of living systems, researchers have engineered cells as independent functional materials or integrated them within a natural or synthetic matrix to create engineered living materials (ELMs). However, the 'livingness' of cells in such materials poses serious drawbacks, such as a short lifespan and the need for cold-chain logistics. Bacterial spores have emerged as a game changer to bypass these shortcomings as a result of their intrinsic dormancy and resistance against harsh conditions. Emerging synthetic biology tools tailored for engineering spores and better understanding of their physical properties have led to novel applications of spore-based materials. Here, we review recent advances in such materials and discuss future challenges for the development of time- and cost-efficient spore-based materials with high performance.

Antibacterial Polymers Based on Two Orthogonal Binding Motifs Coalesce with Bacterial Matter

Addressing the growing concern about antibiotic-resistant bacteria, we have developed a series of polymers exhibiting intrinsic antibacterial activities with a dual-targeting system that induces physical lysis upon copolymer coalescence with bacterial matter. These polymers are equipped with two orthogonal binding motifs that form electrostatic interactions and dynamic covalent complexes on bacterial surfaces and exhibit potent antibacterial activity against Gram-positive and Gram-negative bacteria. The effect of the chemical composition and architecture of copolymers incorporating phenylboronic acid and quaternary ammonium groups on the antimicrobial activities was systematically examined. This work expands the current chemical repertoire to combat antimicrobial resistance by intrinsically antibacterial polymers with a unique mode of action.

Stressor-Actuated Proximity Labeling for Reporting Cellular Interaction

Cell-cell interactions determine the activation state and function of cells. When host cells are exposed to stressors such as microorganisms, immune defense machinery is activated to release H2O2, providing direct evidence of the relevant cellular physiological processes. Inspired by the fact that peroxidase can catalyze proximity labeling in the presence of exogenous H2O2, a stressor-actuated proximity labeling (SAPL) strategy is developed to report the process information on cell-cell interactions by recording stress levels. The stressors are covalently modified with horseradish peroxidase (HRP) and the H2O2 released by the host cells in response to the stressors triggers HRP-based proximity labeling. Using a fungal mimic or live fungi as stressors, the stress levels of different host cells are compared by in situ imaging of the labeling signals. The ability to accumulate stress signals allows SAPL to more sensitively differentiate between interactions involving different macrophage phenotypes. SAPL is also a powerful tool for real-time, in situ monitoring of the effects of surface modifications on cellular interactions. Thus, the SAPL strategy represents a new perspective in the monitoring of cell-cell interactions using endogenous effector molecules.

Macroscopic Assembly of Materials with Engineered Bacterial Spores via Coiled-Coil Interaction

Herein, we report macroscopic materials formed by the assembly of engineered bacterial spores. Spores were engineered by using a T7-driven expression system to display a high density of pH-responsive self-associating proteins on their surface. The engineered surface protein on the spore surface enabled pH-dependent binding at the protein level and enabled the assembly of granular materials. Mechanical properties remained largely constant with changing pH, but erosion stability was pH-dependent in a manner consistent with the pH-dependent interaction between the engineered surface proteins. Our finding utilizes synthetic biology for the design of macroscopic materials and illuminates the impact of coiled-coil interaction across various length scales.

Walking Dead Macrophage-Based Positive Enhancement MRI for Ultrahighly Efficient Diagnosis of Nephritis

Nephritis is an inflammatory condition of the glomerulus, and the clinical gold standard for its diagnosis is a kidney biopsy. However, obtaining biopsy results can take several days, which does not meet the requirement of rapid diagnosis, especially for rapidly progressive types. To achieve an effective and noninvasive diagnosis, we propose a nephritis-specific, positive magnetic resonance imaging (MRI) contrast agent based on Gd3+ anchored walking dead macrophage Gd-RAW. Gd-RAW exhibits high selectivity for inflammatory renal parenchyma and provides comparable results to histopathology methods. The Gd-RAW-based MRI contrast agent reduces the diagnostic time of nephritis from 14 days of biopsy to 1 h. Furthermore, in a unilateral nephritis model constructed by increasing the glycerol concentration, the T1WI of renal parenchyma exhibits an increased signal-to-noise ratio, which is crucial for evaluating nephritic severity. This work promotes rapid diagnosis of nephritis and potentially provides sufficient evidence for clinicians to offer timely treatment to patients. The methodology of paramagnetic ion-anchored macrophage corpse also opens up new prospects for designing more specific and biosafe MRI contrast agents.